1. Technical Field
The present invention relates generally to a method and apparatus for voltage regulation, and more specifically to methods and apparatuses for regulating voltage in computer hardware to compensate for one or more parasitic impedances.
2. Background Art
Many electronics systems employ a DC-to-DC converter to change one voltage to another. Typically, the DC-to-DC converter acts on a supply voltage to produce an input voltage. The input voltage and supply voltages are both direct current (DC) voltages. For example, many computing applications employ a DC-to-DC converter to step down a high supply voltage to a desired input voltage, which is then used to power a microprocessor such as a central processing unit (CPU), microprocessing unit (MPU), application-specific integrated circuit (ASIC), and so forth (collectively, a “load”).
Computer hardware is typically voltage intolerant. That is, computer hardware requires a relatively small input voltage to operate, which must be within a relatively constrained voltage range. Changes to the input voltage of 40 or more millivolts may cause erratic operation of the hardware or even hardware failure. Accordingly, the input voltage to the load must be carefully regulated.
Modern computer hardware is extremely complex and miniaturized. The dual trends of complexity and miniaturization also render computer hardware more vulnerable to parasitic impedances. For example, trace or pattern resistances, interference from adjacent hardware, trace or pattern inductance, and dielectric capacitances may all result in a parasitic impedance affecting the operation of a load. Such impedances may occur inside the load itself, or on the board on which the load is formed or mounted.
Parasitic impedances generally drain a portion of the input voltage, lowering the input voltage seen and utilized by the load. Accordingly, the operation of the load may become unpredictable. The load may operate erratically or not at all, depending on the impedances and voltage tolerance of the load. Further, the parasitic impedances may vary with time, thus complicating regulation of voltage to the load.
Prior art voltage regulators, such as the implementation 100 shown in FIG. 1, employ a voltage sensing amplifier 120 to measure a voltage across the load 102. The output of the voltage sensing amplifier 120 is fed to a compensation amplifier 122, which compares the output to a reference voltage 124. The reference voltage 124 typically equals the desired input voltage for the load 102. Differences between the output of the voltage sensing amplifier 120 and reference voltage 124 cause the compensation amplifier to vary an input to the DC-to-DC converter 104 in order to adjust the input voltage provided by the converter.
However, and as shown in FIG. 1, this prior art implementation fails to account for the presence of parasitic impedances 112, 188. By driving the input voltage to match the reference voltage 124, the prior art regulator 100 ensures the voltage across the load 102 will never equal the reference voltage. The parasitic impedances 112, 118 operate to diminish the load voltage. Thus, the prior art voltage regulator 100 may not allow optimal operation (or operation at all) of the load 102.
Accordingly, an improved voltage regulator is needed.